Amazon RDS for PostgreSQL supports Outbound Network Access using Custom DNS Servers
Amazon RDS for PostgreSQL now supports custom Domain Name Services (DNS) servers which are used for name resolution during outbound network access. This is in addition to the existing support for the Amazon Route 53 domain service in your VPC.
You can configure a custom DNS Server in the DHCP Options Set for the Amazon VPC that contains your RDS instance. For more information, see DHCP Options Sets in the Amazon VPC documentation, and DHCP Options Set in the AWS Directory Service documentation.
You can enable the configured custom DNS server with a new database parameter for your RDS for PostgreSQL databases to communicate with other services within your VPC. This works by using either private or custom DNS names, keeping outbound network traffic within the boundaries of your VPC.
Your RDS for PostgreSQL database instance needs to be in a VPC to be able to use this feature. To move your non-VPC RDS databases to a VPC, follow the instructions in the documentation.
For using custom DNS server for outbound network access for RDS for PostgreSQL, please visit the documentation page.